Carrier-wave call-signaling system



Jan. 8 1924.

J. s. JAMMER CARRIER WAVE] CALL SIGNALING SYSTEM Filed Dec. 29, 1920 Wye/flarc/acob 3 Jam/776k b W4? WW9.

Patented Jan. 8, 1924. I

UNITED STATES PATENT OFFICE.

JACOB S. JAMMER, OF NEW YORK, N, Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., CORPORATION OF NEW YORK.

CARRIER-WAVE CALL-SIGNALING SYSTEM.-

Application filed December 29, 1920. Serial No. 433,748.

To'all whom it may concern: 'to provide a closed circuit signaling system, Be it known that I, J ACOB S. J AMMER, a in which the signal is not actuated upon failcitizen of the United States, residing at New ure of the power supply. 55

York, in the county of New York and State A further object of the invention is to pro- 5 of New York, have invented certain new and vide a closed circuit signaling system in useful Improvements in Carrier-Wave C'allwhich the signal is actuated only in conse- Signaling Systems, of which the following quence of a change of condition, at a predeis a full, clear, concise, and exact description. termined frequency, of the normal transmise 1' This invention relates to a carrier wave sion.

signaling system, and more particularly to The invention utilizes as an essential ele a closed circuit signaling system which inment a slow-acting relay, by which is meant cludes fiieans for preventin ,the actuation of a relay so designed as to require a relatively the signaling means when 518 power fails. long time for energization or deenergization 05 For the purpose of the present description of its actuating winding. The expression a closed circuit signaling system may be islow-acting will be used to distinguish characterized as one in which signaling means from a vibrating type of relay which can be at a receiving station is actuated by reason energized or deenergized su'fiiciently during of an interruption or change of condition of a single cycle of a low frequency interrupa normal energy flow between the sending tion to either operate or release its armature.

20 and receiving signaling circuits. Probably, By proper proportion of the moving elethe simplest arrangement for the accomments, as well as by proper design of the plishment of the signaling function by a magnetic circuit, a relay embodying the closed circuit system is that in which a norsame mechanical and electrical elements as mally transmitted current holds up a relay! in a vibrating type can be made sufiiciently 25 except when the circuit is interrupted, when slow to actuate so that a definite period of the deenergization of the receiver relay retime is required for it to pull up its armasults in the closing of a local ringing circuit. ture A periodic current of longer period A signaling system of this kind is adapted will cause the relay to operate in unison to be used with that common type of modutherewith; a periodic "current of shorter so lated carrier current transmitting system period will not affect the relay. If used with in which the desired low frequency currents, an associated vibrating relay which makes which may be telephonic currents, are transand breaks its circuit at a rate above this mitted as modulations of a carrier current limiting frequency, it may be considered as 86 which is continuously transmitted, the signal slow-acting as compared with the vibrating 35 being actuated upon interruption of the carrelay. This vibrating relay controls the cirrier current. The system may equally well cuits of two slow-acting relays in such manbe used in voice frequency signaling sysner as to cause the call indicator .at the retems or in other systems in which there is ceiver to operate if the interruptions occur 90 normally a continuous transmission of enat a certain rate to which the vibrating relay ergy to the receiver. In signaling systems responds. A single actuation of the vibratof the kind described, a single break or ining relay as in the case of failure of power terruption of the normal flow of the current controls the slow-acting relays so that the will result in a continuous actuation of the call indicator is not operated. signal, as long as the interruption continues. In the drawing Fig. 1 shows a deta led While this is desirable in thecase of a normal circuit arrangement at a, receiving station, signaling operation, since it makes for a simand Fig, 2 shows schematically one means plicity of the circuits and manipulation, it for effecting the periodic interruptlon of a renders the system subject to undesirable normal transmission. The principal subdisturbances whenever the normal transdivisions of the system will be designated mission fails on account of a break in the by reference characters which are sug stransmission cir u t r otherwise. tive of the functions of the elements so 1 en- .It is th pr n pal object of this inveniton tified, For example, the capitalsl), A, ML

LN are used to designate respectively, detecto-r, amplifier, main line and low frequency net work.

Referring to F i 1, a main line or carrier current circuit ML and a local line or low frequency circuit L, balanced respectively by networks HN and LN,are connected for two-way call transmission. As shown there is included in line llllL a hybrid coil of well lrnown type, to the series winding of which is connected the input circuit of a thermionic detector l). Detector 1D functions in the usual manner as a demodulator to analyze the complex high frequency wave impressed on its input into separable components, the low fre uency component of which corresponds in a l respects to the modulating current. The output current of the detector, which includes the carrier and low frequency components, is transmitted by means of transfoer 3 to amplifier A from which amplified energy is transmitted by transformer to circuit 5. A low pass filter F suppresses the carrier frequency component and passes the detected low frequency wave which enters the low fre uency line L through the balanced circuit L common space current source-6 and filament energizing source 7 are provided for the detector and am lifier elements. The system may be varie in many ways from that shown without violating any of the essential principles of the invention which requires merely the continuous presence of a current at the receiver. This element is here furs nished by the carriercomponent which is continuously transmitted whether or not the system is being used to transmit modulated currents.

The circuits 1 and 2, associated with hybrid coils HE and LB respectively, are provided in order that a transmitting branch circuit "may be connected in balanced rela tionship to the receivin circuit between the carrier current circuit and the low frequency circuit L.

Considering now the invention as applied to the above described system, the circuit 8, in shunt to the amplifier output, is resonant to the carrier frequency and accordingly a large part of the carrier current is transmitted through this circuit and through transformer 9 coupled thereto to thermionic relay lit. The relay R has an input circuit 10 also tuned to the carrier frequency. This relay operates in a well lmown manner to receive trains of carrier frequency waves and to vary the amplitude of the unidirectional current traversing a relay 12 in its output circuit for the duration of each carrier wave train. Relay 12, accordingly, during the interval of carrier current flow, holds up its armature 1'2 and completes a circuit through the winding of relay 1%. Relay 1% when tnaoaoo energized, maintains circuit closer 14C in a closed condition. Circuit closer 1a is' in circuit with the winding of relay 18 which circuit also contains a circuit closer 16, 17 which is closed when the movable contact ofrelay 12 is released by interruption of the current through its winding. Relays 13 and 18 are slow-acting in the sense of being slow to release. They will accordingly be sometimes designated as slow-release relays. Relay 12 is quick-acting and is capable of vibrating at the usual ringing frequency.

When the carrier current is periodically interrupted at the transmitting station, as by meanswhich will will be hereinafter described, the armature 17 will vibrate at a corresponding frequency between fixed contacts 15, and 16. Relay 13 is sufficiently slow-acting to maintain circuit closer 14 in actuated position during the interval that,

contact 17 travels from contact 15 to contact 16 and back to 15. The vibrating relay ac cordingly alternately connects relay 13 and relay 18 to ground. Relay 18 is sufliciently energized by the intermittent energization of its winding to maintain the low frequency line L continuously across the local ringing source in circuit 19. @r the relay 18 may be considered as sufficiently slow to release to hold up its armature during the .interval while the contact 17 is out of contact with 16. In the event of a failure of power, the relay 12 will release its armature 17 which will fall back and thereafter maintain contacts 16, 17 closed. After a suliiciently long interval the relay 13 will release its armature and open the circuit through relay 18. Relay 18 is so designed as to be slow torespond, as well as slow to release and is made sufficiently slow to respond that its circuit is opened at 14 before it can connect the line L across the ringing source. Hence, a failure of power is not attended by even a momentary signal actuation.

Figure 2 shows schematically one means for producing a periodic interruption of carrier current. The circuits shown are adapted to cooperate with the receiving circuits which have been described. Obviously similar circuits may be applied at the station illustrated in Fig. 1 in the transmission channel connected to circuits 1 and 2 between the. main line ML and low frequency line L. The parts L, LB, LF, LN and 5 accordingly are similar to the correspondingly indicating elements in Fig. 1, only the circuits associated with the low frequency balanced. circuit being shown. Low frequency impulses from line L are, for normal transmission, transmitted through the balanced circuits LB and used to modulate the carrier frequency current supplied by generator G, the output current of modulator M being transmitted over M and in effect interrupts the carrier cur-' rent. i

Although the invention has been specifically described as applied to a particular form of modulated carrier current system, it should be understood that the efficient operation of the signaling system is dependent in no Way on the particular carrier cur rent system with which it may be used provided only that the current is continuously transmitted. The principle of the invention may equally well be applied to a signaling system in which the continuously transmitted current has no function other than to operate the relay apparatus. It is equally applicable to multiplex carrier transmission in which a plurality of different frequency carrier waves are transmitted over a common transmission line having individual relay apparatus controlled by each carrier wave.

What is claimed is:

1. A signal transmission system comprising a transmission medium, a signal element associated with said transmission medium, means for normally transmitting energy individual to said signal element continuously over said medium, means for actuating said signal element, and means dependent only upon the interruption of said normally transmitted energy for preventing the actuation of said signal element.

2. A closed circuit signaling system comprising a receiver including a signal element, means for causing continuous flow to said receiver of current individual to said signal element, means responsive to said current for normally preventing the actuation of said signal element, and an additional means dependent only upon failure of said current individual to' said signal element for preventing the actuation of said element.

3. A system adapted for signaling by modulated current comprising means for continuous transmission of an unmodulated carrier wave component, a signal, means energiied by said unmodulated component for normally preventing the actuation of the signal, and additional means associated therewith for preventing the actuation of the signal solely by the failure of said unmodulated component.

4. A closed circuit signaling system comprising a receiver, means for causing continuous flow of current to said receiver,

means responsive to said current for normally preventing actuation of the signal and additional means for preventing the actuation of the signal except by an interruption of said current at a predetermined frequency.

5. A system adapted for signaling by modulated carrier current comprising means for continuous, transmission of an unmodulated carrier wave component, a signal means energized by said unmodulated component for normally preventing the actuation of the signal, and additional means for preventing the actuation of the signal except upon interruption of said unmodulated component at a predetermined frequency.

6. In a closed circuit signaling system,

in combination, a transmitting station, a receiver station including a low frequency line, means for causing a continuous flow of current, to the receiving station, means at the transmitting station for periodically changing the condition of said current, a vibrating relay at the receiving station responsive to changes in condition of said current, a local ringing source, a slow-release relay for connecting the low frequency line to said source, a slow-acting relay, and means associating said relays whereby said slow-release relay is maintained in actuated condition only when the condition of said currents periodically changes according to a particular frequency.

7. The combination specified in claim 6 in which the said slow-release relay is also slow to respond.

8. In a closed circuit signaling system, in combination, a transmitting and a receiving station, the latter including a low frequency line, means for causing a continuous flow of current from the transmitting to the receiving stat-ion, means at the transmitting station for periodically interrupting said current, a vibrating relay at the receiving station. responsive to the interrup tions of said current, a local signaling source, a slow-release relay for connecting said low frequency line across said source, a slow-acting relay, and means associating said relays whereby said slow-release relay is maintained in actuated condition only when said current is periodically interrupted according to a predetermined frequency.

9. The combination specified in claim 8 in which the said slow-release relay is also slow to respond.

10. A closed circuit signaling system, comprising means for continuous transmission of power, a receiving circuit, 1ncluding a low frequency line, a slgnal means for preventing the actuatlon of the signal on failure of the power means for periodically interrupting the normal transmission of energy to the receiver, a vibrating relay at the receiver responsive to said interruptions, said relay including a grounded movable contact and two fixed contacts operatively arranged with respect to said movable contact, a slow-release relay in circuit with one of said fixed contacts and ground, a slow release relay in circuit with the other of said fixed contacts and ground and adapted to connect the low frequency line across a local ringing source, a circuit closer interposed in said last mentioned circuit between said vibrating relay and the last mentioned slow-release relay and adapted to be actuated to closed position when said first mentioned slow-release relay is energized, said slow-release relays being so designed as to hold up their armatures when the energizing currents therethrough are interrupted at substantially the frequency of said interrupting means, whereby the signal is actuated only when there is a periodic interruption of the normal trans-- mission according to this frequency.

11. The combination specified in claim 10 having the second mentioned slow-release relay sufiiciently slow to respond so that on failure of power the first mentioned slowrelease relay breaks the circuit through said second mentioned relay before the latter is sufiiciently energized to actuate the signal whereby failure of power does not affect the signal.

12. lin a call signaling system, a common transmission medium, means to impress carrier waves on said -medium,'means to periodically withdraw said waves from said medium at a predetermined rate, a receiving station, a signal at said receivin station, and means responsive to said carrier waves at said receiving station for actuating said signal and responsive only toa predetermined rate of withdrawal of said waves. i

13. A call signal system comprising a. transmission circuit, a relay, a movable eement controlled by said relay to occupy either of two positions according as said relay is energized or deenergized, a signal element, means for operating said, signal element, means for applying a carrier wave to said circuit to actuate said relay and means for maintaining said signal element unresponsive when aid movable element remeans in either of its positions.

14. in a carrier wave system, a transmission medium, means to impress carrier waves on said medium, means to periodically withdraw said waves from said medium at a predetermined rate, a receiving station. a signal at said receiving station, a two-position relay maintained in one of its positions by the incoming carrier wave and in the other position by means operated when the carrier wave is withdrawn, and another relay adapted to cooperate with said two-position relay to prevent an indication by said signal when said two-position relay remains in lay is changing position at the predetermined rate of interruption of said carrier wave.

16. in a carrier wave signaling system, a transmission line, means to impress carrier waves upon said line, means to periodically withdraw said waves from said line at a predetermined rate, a receiving station, sig naling means at said receiving station, arelay responsive to the withdrawal of said carrier waves having a front and back contact corresponding respectively to its actuated and unactuated position and means to prevent a signal indication when said relay is in either its actuated or unactuated position.

17. in a signaling system, an electroresponsive device, an actuating circuit therefor open at a plurality of points and a plurality of relays. cooperating upon the energization of all and subsequent intermittent deenergization and energization of one at a predetermined periodicity, to close said circuit intermittently toactuate said electroresponsive device continuously.

18. lln a signaling system, an electron:- sponsive device, an actuating circuit therefor open at a plurality of points, and a plurality of relays, cooperating uponthe energization of all and subsequent intermittent deenergization and energization of one at a predetermined periodicity, to maintain said actuating circuit continuously closed at one point and intermittently closed at another point to actuate saidelectroresponsive device continuously.

19. A multiplex transmission system comprising a common transmission circuit, means for simultaneously supplying thereto a plurality of different frequency waves, an indicating device, means -to operate said device upon interruption of a given wave and means, dependent solely "upon the fail- .ure of the means for supplying said given wave, for preventing false Operation of said device.

20. A multiplex signaling system comprising false operation of said device in conseing a. common transmission circuit, means quence of the failure solely of the means for 10 for simultaneously supplying thereto a plusupplying said given carrier wave. rality of different frequency carrier waves In witness whereof, I hereunto subscribe 5 each modified in accordance with an indimy name this 22nd day of December A. D.

vidual message, a calling device, means to 1920. operate said device upon interruption of a given carrier wave, and means for prevent- JACOB S. JAMMER. 

